Humans Age at Same Rate as Chimps, Gorillas

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With our clothing, high-rises, technology and more, we humans
would seem to be animal kingdom outsiders, existing outside the
norm. But despite all our advances, it turns out we age and die
at the same rate as other primates.

The finding, published in the latest issue of Science,
shows how strong our ties to chimpanzees, gorillas and other
primates is and counters the long-held belief that, with our
relatively long life spans and access to modern medicine, we age
more slowly than other animals.

"We are making a conceptual point that humans are really very
much more similar in their aging patterns to other primates than
anyone had suspected before," co-author Susan Alberts, a
professor of biology at Duke University, told Discovery News.

"Humans have been a bit of an enigma," added project leader Anne
Bronikowski. "We live much longer than would be expected based on
our body sizes, our morphology, our maturation rates, and our
reproduction rates. When comparisons have been made between
humans versus lab or domestic animals (such as horses, dogs, rats
and mice) humans have had slower rates of aging than these other
species."

But no one until now had previously brought together detailed
datasets on aging and mortality for multiple wild-living
primates, and compared those to data on humans.

Bronikowski, an associate professor in the Department of Ecology,
Evolution and Organismal Biology at Iowa State University, and
her colleagues combined data from long-term studies of humans and
these wild primates: capuchin monkeys from Costa Rica, muriqui
monkeys from Brazil, baboons and blue monkeys from Kenya,
chimpanzees from Tanzania, gorillas from Rwanda, and sifaka
lemurs from Madagascar.

All of these primates and humans, experience high infant
mortality, followed by a period of low mortality during the
juvenile stage and an extended period of increasing age-specific
mortality during mid to late life. These patterns apply to many
animals, however, so the researchers took their analysis of
primates a step further by focusing on the initial mortality rate
(IMR) and the rate at which the probability of dying increases
with age.

"We found that human females cluster with gorillas in infant
mortality, and that human females cluster with chimps, sifakas,
baboons, and muriquis in their rate of aging, so human females
are really right in there with other primates in these two
measures," Bronikowski said.

Men, on the other hand, appear to age more slowly than males of
primate species in the wild, but the differences are minimal,
according to the scientists.

"There is no evidence there that would make a person say, 'Wow,
human males look really unique in their aging patterns,'"
Bronikowski continued. "Moreover, the human males share similar
aging features with the females of other primate species in this
study."

It's clear that two factors increase overall primate life
expectancy.

"Being female and being in a species where male-male competition
is less intense are both good for longevity apparently," Alberts
said.

Co-author Karen Strier of the University of Wisconsin-Madison
explained that muriquis were the only species in the sample in
which males do not compete overtly with one another for access to
mates. This seems to benefit muriqui males, which age more slowly
than other male primates do and live longer than other monkeys.

Caleb Finch, a professor of gerontology at the Ethel Percy Andrus
Gerontology Center, authored a paper published in 1990 that
showed some monkeys have rates of aging as slow as humans do and
that infant mortality can vary widely within populations.

"I am glad to see an expanded analysis which more fully documents
the environmental influence on human and primate mortality during
aging," he told Discovery News. "This and future studies are
relevant to the future of human lifespans.